Apparatus for grading stone



Oct. 21, 1941. c STEVENS I 2,260,095

APPARATUS FOR GRADING;STONE Filed Nov. 30, 1940 2 Sheets-Sheet 1 INVENTOR.

, 7T' j f/iaw'r? CI dizyms Oct. 21, 1941. M. c. STEVENS APPARATUS FOR GRADING- STONE 2 Sheets-Sheet 2 Filed Nov. 30, 1940 m H mm Q My m a WK 7, 4 Z

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gregate will be carried by an elevator to the top of the grading tower. The elevator may be of conventional construction comprising a continuous belt provided with elevator strips I2. The belt is mounted upon rollers M to be driven in a manner which is well understood by suitable power means not here illustrated. The stone may be brought to the bottom of the elevator in any desired manner and the elevating mechanism is provided with side rails 16.

From the top of the elevator the stone aggregate IB is dropped into a hopper at the top of the grading tower. The bottom of the hopper serves as an apron 22 upon which the stone is dropped to slide into a vertical chute or downward passageway 24. The grading tower is shown as having a front wall 26, side walls 28 and. the chute or passageway 24 is provided with a rear wall 30.

At intervals there are provided striker plates 32. Three are here shown arranged vertically spaced throughout the height of the tower. These striker plates are relatively thick, strong metal plates. Mounted upon suitable supports within the tower the striker plates project angularly across the passageway 24 as shown particularly in Fig. 3. There is sufiicient clearance as shown at 34 in Fig. 3 to provide for the angle of these plates being adjusted. Adjusting mechanism 36 is illustrated whereby the angle of the plates may be adjusted. As'shown, these plates extend across the downward passageway at an angle less than 90 to that of the line of fall of the aggregate.

Spaced from each striker plate 32 is a cooperating barrier plate 38. This barrier plate is mounted upon supports .within the tower for adjustment toward and away from the striker plate and for adjustment vertically with respect to the striker plate. The barrier plate is on the opposite side of the stream of aggregate from the striker plate. The rear wall of the passageway 24 is cut away above the barrier plate to provide an opening thereabout. is cut away as at 40 in Fig. 3 so that stone striking the striker plate 32 may rebound out of the downwardly moving stream of aggregate over the barrier plate 38 and through the opening above the barrier plate so as to fall into a receptacle 42 as shown in Fig. 3.

As stated in the preceding paragraph, the barrier plate 38 may be adjusted toward and away from the striker plate. This may be accomplished by the adjusting mechanism illustrated particularly in Figs. 1 and 3. A crank 44 is shown as threaded into a bale 46 which bale like element is secured to the barrier plate 38 as illustrated particularly in Figs. 1 and 2. The crank is rotatable but the end is fixed as at 48 so that upon rotation of the crank the bale like element 46 is moved to adjust the barrier plate toward or away from the striker plate.

This barrier plate is'also adjustable vertically as to height with respect to the striker plate. In the embodiment shown all the barrier plates are connected for vertical adjustment though'it is obvious that they might be individually adjustable. In the construction illustrated there is an adjustment crank 50 upon which is wound a cable 52. The ends of this cable are secured to the bale structure 46 on opposite sides of the barrier plate 38 so that as the crank is rotated the bar- Such rear wall I rier plate will be raised or lowered. It may be held at adjusted positions by dog 54 held by'a spring 56 against a spur wheel 58 mounted on the crank. From the uppermost bale like element 46 cables 60 depend to the intermediate bale like element 46a and from such bale like element to the cables 62 depend to the lowermost bale like element 46b.

It will be noted that sides of the tower are cut away as at 64 to permit such vertical adjustment of the barrier plates and that clearance is provided at 66 so that the fore and aft adjustment mechanism may be raised and lowered with the barrier plates.

A sloping screen 68 extends from adjacent the bottom of each barrier plate downwardly and forwardly toward the chute 24 below the space between the barrier plate and the striker plate so as to direct any material falling on the screen and of such a size as not to pass through the screen back into the chute 24 to continue on downwardly and strike the striker plate therebelow. A certain amount of fine material will pass through this screen mesh into a chute 10 which extends underneath'the screen and discharges into a vertical chute 12 so that the fine material passing through the screen is collected at one place. It will be seen that .each striker plate and barrier plate has such a screen 68 and that delivery of the fine material sifted through the different screens is collected at one place as at 14.

That portion of the aggregate which does not rebound over the barrier plates for collection at 42 and which does not pass through the screens but slides thereover is collected at 16 as shown in Fig. 3. This is the portion of the aggregate which contains the soft stone above a size which will pass through the screens and that portion of the stone of sufficiently low density so that it has not rebounded out of the screen for collection at 42.

The hard dense stone which rebounds out of the stream by virtue of striking the striker plate passes over the barrier plates 38 and is collected at 42 will be found to contain a very small percent, substantially less than 3%, of what might be termed soft stone.. 1

It is desirable to keep the striker plates clean and free from the collection of a soft deposit which might collect thereon and for this purpose a shower system is provided. A shower pipe 18 extends along the rear wall '30 of the chute and in position to direct a spray upon the striker plate 32 all as shown in Figs: 3 and 4. These shower pipes are 'fed from an upright delivery pipe from a suitable source of water pressure and the direction of this shower not only keeps the striker plate clean and free from the deposit so that the dense stone striking it will rebound with suflicient force to fly over the barrier plate but also serves to keep thescreen free and clear.

It is apparent that aggregate in different quarries varies as to density and hardness-and for this reason it may be desirable .to adjust the angularity of the striker plate and to adjust the position of the barrier plate with respect to the striker plate both horizontally and vertically and through the adjustment mechanism heretofore described this may be readily'accomplished.

It is also desirable that the material be fanned out into a relatively thin flowing stream so that the separate rocks will not interfere with each other in their individual response as they strike the striker plates and to assist in this vertical separatorstrips 82 are provided as shown particularly in Figs. 2 and 4. Three are shown in Fig. 2.

These assist in maintaining the, distribution of the stream throughout the entire length of the striker plate. These separator strips are of increased width at the openings in the wall 36 of the downward passageway 24 as shown in Fig. 3. This increased width is as great as the innermost position of the barrier plate 38 will admit and affords a guide to the stone rebounding out of the stream.

What I claim:

1. Rock grading mechanism comprising, in combination, a grading tower provided with a vertical passageway therethrough having a width which exceeds by several times the depth from its front side wall to its rear side wall, means for delivering rock to the upper end of said passageway to fall therethrough, a plurality of striker plates spaced apart at vertical intervals along said passageway, each striker plate projecting downwardly at an angle across the passageway from one side wall to the opposite side wall, said opposite side wall provided with an opening throughout its width opposite each Striker plate and into which the striker plate projects, said opening extending spaced above and below the striker plate providing a passageway for rock therethrough, a barrier plate disposed outwardly beyond each opening and spaced from the outer edge of the striker plate, a screen extending from each barrier plate downwardly and angularly to the side wall along the bottom of the opening adapted to pass fine material therethrough and to direct coarse material thereover back into the passageway below the striker plate, and means separating the fine material passing through the screen and the material passed over the screens from that which rebounds over the several striker plates.

2. Rock grading mechanism comprising, in combination, a grading tower provided with a vertical passageway therethrough having a width which exceeds by several times the depth from its front side wall to its rear side wall, means for delivering rock to the upper end of said passageway to fall therethrough, a plurality of striker plates spaced apart at vertical intervals along said passageway, each striker plate projecting downwardly at an angle across the passageway from one side wall to the opposite side Wall, said opposite side wall provided with an opening throughout its width opposite each striker plate and into which the striker plate projects, said opening extending spaced above and below the striker plate providing a passageway for rock therethrough, a barrier plate disposed outwardly beyond each opening and spaced from the outer edge of the striker plate, a screen extending from each barrier plate downwardly and angularly to the side wall along the bottom of the opening adapted to pass fine material therethrough and to direct coarse material thereover back into the passageway below the striker plate, means for directing a spray of water onto each striker plate to wash the same and to fall therefrom onto the screen therebelow, and means separating the fine material passing through the screen and the material passed over the screens from that which rebounds over the several striker plates.

3. Rock grading mechanism comprising, in combination, a grading tower provided with a vertical passageway having a width which exceeds by several times the depth from its front side wall to its rear side wall, means for directing rock into the upper end of the passageway to fall therethrough, a plurality of striker plates disposed in the same vertical plane and spaced apart at vertical intervals along said passageway, each striker plate projecting downwardly at an angle from one side wall toward the opposite side wall, said opposite side wall provided with an opening throughout its width opposite each striker plate and into which the striker plate projects, said opening extending spaced above and below the striker plate providing a passageway for rock therethrough, a barrier plate disposed outwardly beyond each opening spaced from the outer edge of the striker plate and pro-.. viding a rock passageway therebetween, means extending downwardly angularly from each barrier plate to the adjacent side wall of the passageway along the bottom of the opening adapted to direct certain of the rock material passing through the opening between the barrier plate and striker plate back into the passageway below the striker plate, said passageway provided With a plurality of separator strips extending vertically therethrough above each striker plate, said separator strips being spaced apart at intervals throughout the width of the passageway, and means separating the material which rebounds over the barrier plates from that which passes between the barrier plates and the striker plates.

4. Rock grading mechanism comprising, in combination, a grading tower provided with a vertical passageway having a width which exceeds by several times the depth from its front side wall to its rear side wall, means for directing rock into the upper end of the passageway to fall therethrough, a plurality of striker plates disposed in the same vertical plane and spaced apart at vertical intervals along said passageway, each striker plate projecting downwardly at an angle from one side wall toward the opposite side wall, said opposite side wall provided with an opening throughout its width opposite each striker plate and into which the striker plate projects, said opening extending spaced above and below the striker plate providing a passageway for rock therethrough, a barrier plate disposed outwardly beyond each opening spaced from the outer edge of the striker plate and providing a rock passageway therebetween, said barrier plate being adjustable to an innermost position adjacent the striker plate and away from the striker plate, means extending downwardly angularly from each barrier plate to the adjacent side wall of the passageway along the bottom of the opening adapted to direct certain of the rock material passing through the opening between the barrier plate and striker plate back into the passageway below the striker plate, said passageway provided with a plurality of separator strips extending vertically therethrough above each striker plate and projecting through the-opening above the striker plate to the innermost position of the barrier plate, said separator strips being spaced apart at intervals throughout the width of the passageway, and means separating the material which rebounds over the barrier plates from that which passes between the barrier plates and the striker plates.

MARVIN C. STEVENS. 

